Pivotable drive apparatus for a stand-on vehicle

ABSTRACT

A vehicle transmission housing has first and second axle housings pivotably connected to opposite ends of the transmission housing and a stand-on platform may be connected to the assembly. A first gear train in the first axle housing drives a first axle having a first axis of rotation. A second gear train is disposed in the second axle housing drives a second axle having a second axis of rotation collinear with the first axis of rotation. The axle housings are both capable of pivoting about the transmission housing about a third axis that is parallel to the first and second axes. The first and second axle housings may also be separately rigidly or flexibly connected to one another. This assembly permits adjustment of the ground heights of the platform with respect to a vehicle frame.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No.62/422,336, filed on Nov. 15, 2016, U.S. Provisional Application No.62/415,177, filed on Oct. 31, 2016, and U.S. Provisional Application No.62/403,498, filed on Oct. 3, 2016. The contents of these priorapplications are incorporated herein by reference in their entirety.

BACKGROUND

The disclosure herein relates to a compact drive apparatus used inconnection with a stand-on vehicle.

SUMMARY

Stand-on utility vehicles such as lawn mowers are known, and generallyhave a prime mover such as an internal combustion engine mounted on aframe and engaged to and driving a transmission, which may be ahydrostatic transmission. Stand-on vehicle designs are shown incommonly-owned U.S. Pat. No. 9,499,199 and commonly-owned U.S. patentapplication Ser. No. 14/692,970, now U.S. Pat. No. 9,969,258; thedisclosures of both of these references are incorporated herein byreference. It is also known to attach the stand-on platform to the frameof the vehicle in such a manner that the platform can be adjusted todifferent heights.

The pivotable drive apparatuses disclosed herein provide for attachmentof the stand-on platform to one or more components of the driveapparatus. The drive apparatuses include a hydrostatic transmission anda pair of axle assemblies that provides not only a compact design butalso simplifies the installation of the drive, the axles, and thestand-on platform components in the vehicle and allows the user toadjust the ground height of both the vehicle frame and the stand-onplatform simultaneously or alternatively, to adjust the ground height ofthe vehicle frame while maintaining the height of the stand-on platform.

A better understanding of the disclosure will be obtained from thefollowing detailed descriptions and accompanying drawings, which setforth illustrative embodiments indicative of the various ways in whichthe principals of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a drive apparatus inaccordance with the teachings herein.

FIG. 2 is a top plan view of the drive apparatus of FIG. 1.

FIG. 3 is a top plan view of the drive apparatus of FIG. 1, with housingelements removed.

FIG. 4 is a cross-sectional view through the pivot axis of thehydrostatic transmission of the drive apparatus shown in FIG. 3, alongthe line 4-4.

FIG. 5 is a front, elevational internal view of a second embodiment of atransmission for use in connection with a drive apparatus in accordancewith the teachings herein.

FIG. 6 is a front, elevational internal view of a third embodiment of atransmission for use in connection with a drive apparatus in accordancewith the teachings herein.

FIG. 7 is a perspective view of a further embodiment of a driveapparatus in accordance with the teachings herein.

FIG. 8 is a partially exploded perspective view of the drive apparatusof FIG. 7 with certain components removed for clarity.

FIG. 9 is a partially exploded perspective view of the transmissionhousing and portions of the transmission of the drive apparatus of FIG.7.

FIG. 10 is a front, elevational internal view of the transmissionportion of the drive apparatus of FIG. 7.

FIG. 11 is a front perspective view of another embodiment of a driveapparatus in accordance with the teachings herein.

FIG. 12 is a front perspective view of the drive apparatus of FIG. 11,with certain components removed for clarity.

FIG. 13 is a partially exploded, front perspective view of the driveapparatus of FIGS. 11 and 12, with additional components removed forclarity.

FIG. 14 is a plan view of an exemplary vehicle incorporating one of thedrive apparatuses disclosed herein.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the invention in accordance with its principles.This description is not provided to limit the invention to theembodiment(s) described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiment(s) describedherein, but also any other embodiment that may come to mind inaccordance with these principles. The scope of the invention is intendedto cover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers or serial numbers using different prefixes in caseswhere such labeling facilitates a more clear description orunderstanding. Additionally, the drawings set forth herein are notnecessarily drawn to scale, and in some instances proportions may havebeen exaggerated to more clearly depict certain features. Item numbersuffixes “L” and “R” used herein relate to typical “Left” and “Right”orientation of certain components and assemblies as viewed from the rearof a typical stand-on vehicle, and are not limiting as to the scope ofthe invention. This specification is intended to be taken as a whole andinterpreted in accordance with the principles of the invention as taughtherein and understood by one of ordinary skill in the art.

A first embodiment of a pivotable drive apparatus 10 is shown in FIGS.1-4, where drive apparatus 10 comprises a hydrostatic transmissionassembly 20 having a transmission housing 22, and a pair of preferablyidentical final reduction axle assemblies 15L, 15R, each comprising adrive axle 32 disposed in an axle housing 34. Each axle housing 34includes an engagement structure 36. When assembled in drive apparatus10, the two engagement structures 36 are located at the proximal ends ofthe two axle housings 34 adjacent to the center of drive apparatus 10and are illustrated as tab-like structures capable of being connectedtogether by means of fasteners (not shown). Each axle assembly 15L, 15Ralso includes a gear housing 35 formed with or connected to the distalend of each axle housing 34. Each gear housing 35 houses one of a pairof reduction gear trains 45L, 45R as discussed herein.

A pair of output drive shaft housings 41L, 41R is disposed, one toeither side of transmission housing 22, adjacent to gear housings 35.The various housings cooperate to form the drive apparatus 10 to bemounted into a vehicle such as vehicle 300 having a stand-on platform308. It will be understood that vehicle 300 of FIG. 14 depicts anembodiment of the drive apparatus disclosed herein, and in particulardrive apparatus 310 shown in FIGS. 7-10, as described in more detailbelow, but the applicability and use of drive apparatus 10 or the otherdrive apparatuses described herein in a similar vehicle will be known toone of ordinary skill in the art. Various thrust bearings, shaftbearings, fasteners, pistons and the like are depicted in the figuresbut not described herein as these will be understood by one of ordinaryskill in the art.

As shown most clearly in FIGS. 3 and 4, hydrostatic transmissionassembly 20 comprises a pump cylinder block 21 and a motor cylinderblock 23 both rotatably disposed on center section 30. Center section 30includes hydraulic porting therein (not shown) to hydraulically connectpump cylinder block 21 to motor cylinder block 23. Pump input shaft 24is engaged to and drives the pump cylinder block 21, and extends out oftransmission housing 22 where it is driven by a pulley powered by aprime mover in a known manner, such as pulley and belt assembly 305,prime mover 303 and prime mover output shaft 304 as shown in FIG. 14.External control arm 26 is engaged to a trunnion arm 27 for pivoting ofa swash plate 25, thereby controlling the output of pump cylinder block21. Motor cylinder block 23 is formed with a series of slots 23 aarranged about its circumference, and a brake mechanism 39 may beengaged to the slots 23 a by brake arm 28, to provide a parking brake.

Motor output shaft 31 is engaged to and driven by motor cylinder block23, and extends out both sides of center section 30 to drive the pair ofreduction gear trains 45L, 45R. A pair of clutch assemblies 33L, 33R isprovided, one on each end of motor output shaft 31, to permit theoperator to clutch one side of drive apparatus 10 or the other, or toapply a braking force to one side of drive apparatus 10 or the other, toenable steering of the stand-on vehicle. Each of the clutch assemblies33L, 33R connects an end of motor output shaft 31 to a respective outputdrive shaft 37L, 37R, and each output drive shaft 37L, 37R is engaged toa respective gear train 45L, 45R. A pair of operator levers 29L, 29R isengaged to the pair of clutch assemblies 33L, 33R, to permit theoperator to engage each clutch assembly 33L, 33R independently ortogether, using appropriate linkages (not shown).

Each of the pair of reduction gear trains 45L, 45R terminates in a maingear 51 which drives a respective hub 38L, 38R for attachment of avehicle wheel such as driven wheel 306 of FIG. 14, and further comprisesa pinion gear 57 disposed on the end of an output drive shaft 37L or37R, and a combination reduction gear 58 mounted on a jack shaft 60.

The output drive shafts 37L, 37R are illustrated herein as being ofequal length. A vehicle manufacturer may instead select differentlengths for these components (and associated output drive shaft housings41L, 41R) in order to shift the location of pump input shaft 24 towardone side of a vehicle or the other to achieve a desired drive beltrouting, linkage configuration, etc.

A benefit of having the two axle assemblies 15L, 15R separable, and yetcapable of being joined by means of the pair of engagement structures36, is that it allows the vehicle manufacturer to manipulate the twosides of drive apparatus 10 separately for ease of installation, andthen to connect the two axle assemblies 15L, 15R together when placed inthe vehicle, to provide improved rigidity and axle alignment. Each axlehousing 34 includes an attachment structure 49 for attachment of avehicle's stand-on platform directly to the drive apparatus 10. A simplemodification of stand-on platform 308 shown in FIG. 14 will accommodateattachment of platform 308 to attachment structures 49. A simple offsetbar (not shown) or other extension component can be added between thepair of engagement structures 36 to increase the overall width of driveapparatus 10 for versatile use in more than one vehicle model. Acorresponding adjustment in length of one or both of the output driveshafts 37L, 37R and associated output drive shaft housings 41L, 41R isneeded if the overall width of drive apparatus 10 is adjusted. The driveapparatus 10 is mounted in the vehicle so as to be pivotable about theaxis 10Ax of the motor output shaft 31 so that the ground clearance ofthe vehicle frame may be varied in relation to the axle assemblies 15L,15R, thus also adjusting the position of the stand-on platform inrelation to the frame of the vehicle. That is, the prime mover and thetransmission assembly 20 are mounted to the vehicle frame in a fixedrelationship to one another, while the axle assemblies 15L, 15R can bepivoted about the axis 10Ax of the motor output shaft 31 of transmissionassembly 20. When the axle assemblies 15L, 15R are pivoted in thismanner, this effectively raises or lowers the vehicle frame in relationto the ground, and a corresponding height adjustment may be needed atthe front wheels to maintain an approximately level vehicle frame,mowing deck, etc. A pair of attachment ears 42 is provided to enable theuser to lock drive apparatus 10 into a chosen position once theappropriate adjustments are made.

Alternative embodiments are depicted in FIGS. 5 and 6, and thetransmissions disclosed therein may be used with the drive apparatusdisclosed herein, and in particular may be used in housings similar tothe housing structures discussed above. Structures that are similar toprior structures in appearance and/or function to those previouslydescribed are assigned a similar numeral but with a different prefix.Not every such structure is discussed in detail where the operation orconstruction thereof would be understood by a person of skill in theart. The housings for the embodiments depicted in FIGS. 5 and 6 are notshown in order to clearly depict the internal structures of thetransmissions at issue; it will be understood that these housings wouldbe essentially the same as those depicted in FIGS. 1-4, with certainmodifications that would be known to one of ordinary skill in the art.

More specifically, a second embodiment of a drive apparatus 110comprising hydrostatic transmission 120 is shown in FIG. 5, where twoseparate center sections 130L, 130R are used to mount a pair of pumpcylinder blocks 121L, 121R. The output of each pump cylinder block 121L,121R is controlled by a respective swash plate 125L, 125R, usingrespective control arms 126L, 126R. A single input pulley 170 is engagedto one or the other of pump input shafts 124L, 124R to drive the pair ofpump cylinder blocks 121L, 121R by means of an input gear set 171.

A pair of motor cylinder blocks 123L, 123R is also disposed onrespective center sections 130L, 130R and connected to pump cylinderblocks 121L, 121R through hydraulic porting (not shown) in centersections 130L, 130R. Each motor cylinder block 123L, 123R drives a motoroutput shaft 131L, 131R to drive a reduction gear train 145L, 145R andrespective output axles 132L, 132R and hubs 138L, 138R in a mannersimilar to that described above.

A third embodiment of a hydrostatic transmission 220, also suitable foruse in a pivotable drive apparatus, is shown in FIG. 6, where twoseparate center sections 230L, 230R are used to mount a pair of pumpcylinder blocks 221L, 221R. The output of each pump cylinder block 221L,221R is controlled by a respective swash plate 225L, 225R, using controlarms 226L, 226R. A pulley 270 is used to drive the pair of pump cylinderblocks. A difference from the prior embodiment is that the pumps andmotors in the third embodiment are disposed in a back-to-backrelationship, and pulley 270 drives an input shaft 272 of a T-box stylegear set 271 to power the two pump input shafts 224L, 224R.

A pair of motor cylinder blocks 223L, 223R is also disposed onrespective center sections 230L, 230R and connected to pump cylinderblocks 221L, 221R through hydraulic porting (not shown) in centersections 230L, 230R. Each motor cylinder block 223L, 223R drives a motoroutput shaft 231L, 231R, each having a pinion gear 257 disposed on thedistal end thereof.

A further embodiment of a drive apparatus 310 having a transmissionassembly 320 connected to a pair of final reduction axle assemblies315L, 315R is shown in FIGS. 7-10. Referenced previously herein, FIG. 14depicts the drive apparatus 310 in vehicle 300 having a frame 301supporting a pair of casters 307, and a prime mover 303 mounted onvehicle platform 302. A prime mover output shaft 304 drives pulley andbelt assembly 305 to power the transmission input shaft 372. Vehicle 300is depicted as a stand-on lawn mower and includes a mowing deck 309. Apair of driven wheels 306 is engaged to the two output axles 332L, 332R,the speed and direction of which may be controlled by respective controlarms 326L, 326R engaged to operator controls (not shown). Prime mover303 may be, for example, an internal combustion engine of standard sizeand output for a vehicle such as stand-on mower 300.

A pair of axle housings comprising a pair of axle main housings (or geartrain housings or combination gear train/axle housings) 334 is pinnedtogether and the pair of axle main housings 334 is also connected toopposite ends of hydrostatic transmission assembly 320 in a pivotablemanner by means of interface structures 322 b formed on each end oftransmission main housing 322. Interface structures 322 b are joined bymeans of a slip fit connection to corresponding attachment openings 334b formed in each gear train housing 334, such that each gear trainhousing 334 can pivot about a common axis of hydrostatic transmissionassembly 320, namely the axes of rotation of the two output shafts 331L,331R described below. Such pivoting provides the benefits describedabove with regard to the positioning of the various components invehicle 300. Retaining rings 364 are compressed radially by ramps 334 dduring assembly and, when the drive apparatus 310 is assembled, engagegrooves 334 e to prevent axial movement of final reduction axleassemblies 315L, 315R. Reduction gear train 345L (shown) and reductiongear train 345R (not shown) may be lubricated with grease and sealed atthe slip fit interface by O-rings 365 mounted on the interfacestructures 322 b.

Each gear train/axle housing 334 also includes a pin pocket 334 a forreceiving a joint pin 350, so that the gear train/axle housings 334 areengaged to one another in a manner that improves structural support andaxial alignment of output axles 332L, 332R. Additionally, because thegear train housings 334 are engaged to one another in a somewhatflexible manner (i.e., able to flex about pin 350 and not lockedtogether), ease of assembly is improved in this embodiment. Thisflexible engagement may also permit a limited degree of relativemovement between components of drive apparatus 310 during operation of avehicle such as vehicle 300 over rough terrain, during which flexing mayoccur.

Each gear train/axle housing 334 has an axle housing cover 316 connectedthereto by fasteners 317. While only one is depicted, each geartrain/axle housing 334 includes a connection structure, namely anattachment boss 334 c to secure the stand-on platform 308 of vehicle300. (The pair of final reduction axle assemblies 315L, 315R ispreferably identical.) Drive apparatus 310 may be mounted on vehicle 300by means of a plurality of mounting structures 322 a formed ontransmission main housing 322. A pair of adjustable and lockingconnection mechanisms 390 (represented by a pair of heavy dashed linesin FIG. 14) is provided to both facilitate a vehicle ground clearanceadjustment to vehicle 300 and to secure the stand-on platform 308 in alevel, fixed position relative to vehicle frame 301 once the groundclearance adjustment has been made.

As shown in FIG. 9, a transmission cover 374 is secured to transmissionmain housing 322 by means of fasteners 375 to form an internal sump intransmission assembly 320. A bladder cover 377 is connected totransmission cover 374 by fasteners 378 to cover the bladderinstallation opening 374 a and expansion bladder 340, and comprises anexternal air vent 377 a. The optional expansion bladder 340 is insertedinto opening 374 a and is disposed in the internal sump and is trappedbetween bladder cover 377 and transmission cover 374. A set ofdeflectors 374 b may be installed or formed integrally (as shown) ontransmission cover 374 about the bladder installation opening 374 a toprotect expansion bladder 340 from pressurized fluid flow from bleeds(not shown) formed in the check plugs 380 described below. Hydraulicfluid is retained in the sump of transmission assembly 320 by means ofjoint sealant or gaskets and various seals, such as motor output shaftseals 343.

Referring to FIGS. 9 and 10, a common center section 330 comprises apair of pump running surfaces 330 a on a top surface thereof, on whichthe two pump cylinder blocks 321L, 321R are rotatably disposed. Eachpump running surface 330 a is connected to a respective motor runningsurface 330 b formed on opposite ends of center section 330, where themotor cylinder blocks 323L, 323R are rotatably disposed. As is known, apair of kidney ports on each running surface permits hydrauliccommunication between the respective pump cylinder block and motorcylinder block through porting formed internal to center section 330.Two pairs of check plugs 380 are disposed on the bottom of centersection 330 (one check plug 380 of each pair is shown) to permithydraulic fluid to enter the porting of center section 330. Fasteners367 are used to connect center section 330 to an internal surface (notshown) of transmission main housing 322.

Two pump input shafts 324L, 324R are driven by a pulley 370 and an inputgear set 371, and two motor output shafts 331L, 331R are engaged to anddriven by motor cylinder blocks 323L, 323R. Input gear set 371 is abalanced arrangement comprising three spur gears and having a separateinput shaft 372 driving the central gear of the gear set.

As shown in FIG. 10, a pair of swash plates 325L, 325R is provided forcontrolling output of pump cylinder blocks 321L, 321R, respectively, anda pair of respective external control arms 326L, 326R is used to controlthe arcuate positioning of swash plates 325L, 325R, thereby controllingthe output of pump cylinder blocks 321L, 321R.

Each motor output shaft 331L, 331R drives an output pinion gear 357. Asshown in FIG. 8 (with respect to transmission assembly 320 and finalreduction axle assembly 315L), output pinion gear 357 is connected tomotor output shaft 331L and drives the reduction gear 358 disposed onjack shaft 360. Reduction gear 358 then drives main gear 351 which isengaged to and drives the output axle 332L. The gear train on theopposite side with respect to final reduction axle assembly 315R andoutput axle 332R may be substantially identical thereto.

Input gear set 371 comprises three gears; namely, input gear 371Cengaged to and driven by input shaft 372, right input gear 371R engagedto and driving pump input shaft 324R, and left input gear 371L engagedto and driving pump input shaft 324L. These three gears are disposed ina gear chamber 322 c formed on an external, upper surface oftransmission main housing 322 and are lubricated with hydraulic fluidfrom sump. Input gear cover 318 is secured to transmission main housing322 by means of fasteners 319.

A further embodiment of a drive apparatus 410 is depicted in FIGS.11-13. As before, drive apparatus 410 could be used in a vehicle such asvehicle 300 previously described with minor modifications. As before,similar structure using similar reference numerals but with a differentprefix can be substantially the same as previously described except asnoted herein. Other than the support structures 422 b and provisions forattachment of the final reduction assemblies 411L, 411R as describedbelow, hydrostatic transmission assembly 420 is configured to besubstantially identical to hydrostatic transmission assembly 320described previously herein, and will not be described in furtherdetail. In this embodiment, hydrostatic transmission assembly 420comprising a transmission main housing 422 has two separate finalreduction assemblies 411L, 411R mounted on opposite sides thereof andconnected by means of a hub support shaft 413, which does not rotatewith respect to a vehicle frame such as frame 301 once it is installedin a vehicle, such as vehicle 300, and has a platform, such as amodified platform 308, secured thereto. Hub support shaft 413 couldalternatively be a non-rotatable frame shaft. Each final reductionassembly 411L, 411R comprises a gear hub 412 having a gear flange 412 a.Each gear hub 412 is rotatably mounted on the hub support shaft 413using at least one bearing 462 (two bearings per hub shown) and drivesan output wheel such as driven wheel 306. A reduction chain 459 connectseach output pinion gear 457 with a gear flange 412 a in order to drivegear hubs 412. Each output pinion gear 457 is mounted on and driven byone of motor output shaft 431L on one side or motor output shaft 431R(not shown) on the opposite side. As in prior embodiments, control arms426L and 426R are disposed external to transmission main housing 422,and input shaft 472 extends outwardly therefrom. Mounting bosses 422 aare also provided to connect drive apparatus 410 to a vehicle frame suchas frame 301 of vehicle 300.

In this embodiment, final reduction assemblies 411L, 411R are pivotablyconnected to transmission main housing 422 by means of a pair of pivotarms 414. In FIG. 12, one of the gear hubs 412 and reduction chain 459are removed so that one can more clearly see one of the pivot arms 414.And, as shown more clearly in FIG. 13, each pivot arm 414 includes afirst pivot opening 414 a at a distal end acting as an interface toreceive hub support shaft 413 such that pivot arm 414 can pivotthereabout during vehicle height adjustment (i.e. ground clearance ormowing height adjustment). At its proximal end, each pivot arm 414 alsocomprises a second pivot opening 414 b acting as an interface topivotably connect the pivot arm 414 to support structure 422 b formed ontransmission main housing 422. A groove 414 c formed in each pivot armopening 414 b engages a retaining ring 464 formed in support structure422 b to ensure proper connection of the final reduction assemblies411L, 411R to the hydrostatic transmission assembly 420.

A simple modification of the stand-on platform 308 shown in FIG. 14 willaccommodate attachment of platform 308 to the hub support shaft 413 ofdrive apparatus 410. Similar to the previously described embodiment, apair of adjustable and locking connection mechanisms 390 (represented bythe pair of heavy dashed lines in FIG. 14) is provided to bothfacilitate a vehicle ground clearance adjustment to vehicle 300 and tosecure the stand-on platform 308 in a level, fixed position relative tovehicle frame 301 once the ground clearance adjustment has been made. Itshould be noted that the ground height of the hub support shaft 413 doesnot change, and the modified platform 308 secured to support shaft 413does not necessarily change, when a vehicle ground clearance adjustmentis made. However, a different or additional modification to stand-onplatform 308 (and possibly to connection mechanisms 390) could be madeto accommodate height adjustment of platform 308, if desired for aparticular vehicle configuration.

In this embodiment, a drive apparatus for use in a stand-on vehiclehaving a first driven wheel and a second driven wheel may comprise atransmission assembly comprising a transmission housing with atransmission disposed therein; a first output shaft extending out afirst end of the transmission housing and driving a first output gearand a second output shaft extending out a second end of the transmissionhousing, opposite the first end, and driving a second output gear; afirst gear hub comprising a first gear flange and a second gear hubcomprising a second gear flange. Such a drive apparatus may furthercomprise a first reduction chain extending between the first output gearand the first gear flange and transmitting a first output from thetransmission to the first gear hub; a second reduction chain extendingbetween the second output gear and the second gear flange andtransmitting a second output from the transmission to the second gearhub; an operationally non-rotating hub support shaft extending betweenthe first gear hub and the second gear hub, wherein the first gear hubis rotatably mounted on one end of the hub support shaft and the secondgear hub is rotatably mounted on the other end of the hub support shaft.Such a drive apparatus may further comprise a first support structurelocated on the first end of the transmission housing adjacent the firstoutput gear and a second support structure located on the second end ofthe transmission housing adjacent the second output gear; a first pivotarm having a first proximal end pivotably mounted on the first supportstructure and a first distal end pivotably engaged to the hub supportshaft; and a second pivot arm having a second proximal end pivotablymounted on the second support structure and a second distal endpivotably engaged to the hub support shaft. Such a drive apparatus mayfurther comprise the first gear flange having a first external face towhich the first gear hub is connected, and a first internal faceopposite to the first external face, and the second gear flange having asecond external face to which the second gear hub is connected, and asecond internal face opposite to the second external face, and whereinthe first pivot arm is pivotably connected to the hub support shaftadjacent to the first internal face and the second pivot arm ispivotably connected to the hub support shaft adjacent to the secondinternal face.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof.

What is claimed is:
 1. A drive apparatus for use in a vehicle having afirst driven wheel and a second driven wheel, the drive apparatuscomprising: a transmission housing having a transmission disposedtherein, the transmission driving a first gear train located at one endof the transmission and driving a second gear train located at a secondend of the transmission, wherein the first gear train is disposed in afirst gear housing and the second gear train is disposed in a secondgear housing; a first axle housing connected to the first gear housingand having a proximal end adjacent the center of the drive apparatus anda distal end adjacent the first driven wheel, the first axle housingcomprising a first connection mechanism; a second axle housing connectedto the second gear housing and having a second proximal end adjacent thecenter of the drive apparatus and a second distal end adjacent thesecond driven wheel, and comprising a second connection mechanism,wherein the first axle housing may be connected to the second axlehousing by engagement of the first connection mechanism to the secondconnection mechanism.
 2. The drive apparatus of claim 1, furthercomprising a first attachment structure formed on an external surface ofthe first axle housing and a second attachment structure formed on asecond external surface of the second axle housing, wherein the firstattachment structure and the second attachment structure are located andformed to enable attachment of a stand-on platform to the driveapparatus.
 3. A drive apparatus for use in a vehicle having a firstdriven wheel and a second driven wheel, the drive apparatus comprising:a transmission assembly comprising a transmission housing with atransmission disposed therein, the transmission driving a first geartrain located at a first end of the transmission housing and driving asecond gear train located at a second end of the transmission housing,opposite the first end; a first axle housing pivotably connected to thefirst end of the transmission housing, wherein the first gear train isdisposed in the first axle housing, the first axle housing comprising afirst pin pocket; a first axle extending out of the first axle housing;a second axle housing pivotably connected to the second end of thetransmission housing, wherein the second gear train is disposed in thesecond axle housing, the second axle housing comprising a second pinpocket; a second axle extending out of the second axle housing, whereinthe first axle and the second axle rotate about a first axis ofrotation; wherein the first axle housing and the second axle housingboth are capable of pivoting with respect to the transmission about asecond axis that is parallel to the first axis of rotation; and a pinhaving a first end extending into the first pin pocket and a second endextending into the second pin pocket.
 4. The drive apparatus of claim 3,wherein the first axle housing is flexibly aligned with the second axlehousing about the first axis of rotation.
 5. The drive apparatus ofclaim 4, wherein the first and second pin pockets align the pin alongthe first axis of rotation.
 6. The drive apparatus of claim 5, whereinthe transmission is a hydrostatic transmission comprising a hydraulicpump and a hydraulic motor.
 7. The drive apparatus of claim 3, whereinthe transmission is a hydrostatic transmission comprising a pair ofhydraulic pumps and a pair of hydraulic motors, wherein the pair ofhydraulic pumps and the pair of hydraulic motors are disposed on acommon center section disposed in the transmission housing.
 8. The driveapparatus of claim 7, wherein each of the pair of hydraulic motorscomprises a separate output shaft driven by a separate motor cylinderblock, and each output shaft drives one of the first and second drivenwheels.
 9. The drive apparatus of claim 3, further comprising: a firstinterface structure located at the first end of the transmission housingand a second interface structure located at the second end of thetransmission housing; a first attachment opening formed on one end ofthe first axle housing and shaped to receive the first interfacestructure; and a second attachment opening formed on one end of thesecond axle housing and shaped to receive the second interfacestructure, whereby the first and second axle housings are each pivotablyconnected to the transmission housing.
 10. The drive apparatus of claim3, further comprising a first connection structure formed on the firstaxle housing and a second connection structure formed on the second axlehousing, wherein a platform may be connected to the first and secondconnection structures.
 11. The drive apparatus of claim 3, wherein thefirst axle housing comprises a first axle main housing having a firstaxle housing cover attached thereto and the second axle housingcomprises a second axle main housing having a second axle housing coverattached thereto, wherein the first axle extends out of the first axlehousing cover and the second axle extends out of the second axle housingcover.
 12. The drive apparatus of claim 11, further comprising a firstconnection structure formed on the first axle housing and a secondconnection structure formed on the second axle housing, wherein aplatform may be connected to the first and second connection structures.13. The drive apparatus of claim 12, further comprising: a firstinterface structure located at the first end of the transmission housingand a second interface structure located at the second end of thetransmission housing; a first attachment opening formed on one end ofthe first axle housing and shaped to receive the first interfacestructure; and a second attachment opening formed on one end of thesecond axle housing and shaped to receive the second interfacestructure, whereby the first and second axle housings are each pivotablyconnected to the transmission housing.
 14. A drive apparatus for use ina vehicle having a first driven wheel and a second driven wheel, thedrive apparatus comprising: a transmission assembly comprising atransmission housing with a transmission disposed therein, thetransmission driving a first gear train located at a first end of thetransmission housing and driving a second gear train located at a secondend of the transmission housing, opposite the first end; a first axlehousing pivotably connected to the first end of the transmissionhousing, wherein the first gear train is disposed in the first axlehousing; a first axle extending out of the first axle housing; a secondaxle housing pivotably connected to the second end of the transmissionhousing, wherein the second gear train is disposed in the second axlehousing; and a second axle extending out of the second axle housing,wherein the first axle and the second axle rotate about a first axis ofrotation; wherein the first axle housing and the second axle housing areboth capable of pivoting about the transmission housing about a secondaxis that is parallel to the first axis of rotation; and a means forconnecting the first axle housing to the second axle housing.
 15. Thedrive apparatus of claim 14, wherein the means for connecting permitsthe first axle housing to flex with respect to the second axle housing.16. The drive apparatus of claim 14, further comprising a firstconnection structure formed on the first axle housing and a secondconnection structure formed on the second axle housing, wherein aplatform may be connected to the first and second connection structures.17. The drive apparatus of claim 14, wherein the transmission is ahydrostatic transmission comprising a hydraulic pump and a hydraulicmotor.
 18. The drive apparatus of claim 14, wherein the first axlehousing comprises a first axle main housing having a first axle housingcover attached thereto and the second axle housing comprises a secondaxle main housing having a second axle housing cover attached thereto,wherein the first axle extends out of the first axle housing cover andthe second axle extends out of the second axle housing cover.
 19. Thedrive apparatus of claim 18, further comprising a first connectionstructure formed on the first axle housing cover and a second connectionstructure formed on the second axle housing cover, wherein a platformmay be connected to the first and second connection structures.
 20. Thedrive apparatus of claim 14, wherein the means for connecting the firstaxle housing to the second axle housing comprises a pin having a firstend disposed in a first pin pocket formed in the first axle housing anda second end disposed in a second pin pocket formed in the second axlehousing.